(NIH Excerpts): Scientists at the National Institutes of Health (NIH) have developed a new sample preparation method to detect SARS-Cov-2.

The method bypasses extraction of the genetic RNA material of the virus, simplifying sample purification and potentially reducing test time and cost.

Researchers used a chelating agent made by the lab supply company Bio-Rad called Chelex 100 resin to preserve SARS-CoV-2 RNA in samples for detection by RT-qPCR. They used nasopharyngeal and saliva samples with various virion concentrations to evaluate whether they could be used for direct RNA detection, which it did with very high sensitivity. This preparation also inactivated the virus, making it safer for lab personnel to handle positive samples.

To validate the test, patient samples were collected and stored in either viral transport media, or the newly developed chelating-resin-buffer at the NIH Symptomatic Testing Facility. The samples in viral transport media were tested by the COVID-19 testing team using conventional RNA extraction and RT-qPCR testing. The samples in the chelating-resin-buffer were heated and the viral RNA was, then, tested by RT-qPCR. The new preparation significantly increased the RNA yield available for testing, compared to the standard method.

Standard tests for detection of SARS-CoV-2 involve amplifying viral RNA to detectable levels using a technique called quantitative reverse transcription PCR (RT-qPCR). But first, the RNA must be extracted from the sample. Manufacturers of RNA extraction kits have had difficulty keeping up with demand during the COVID-19 pandemic, hindering testing capacity worldwide.

Robert B. Hufnagel, M.D., Ph.D., chief of the NEI Medical Genetics and Ophthalmic Genomic Unit who co-led the team with Bin Guan, Ph.D., a fellow at the Ophthalmic Genomics Laboratory at NEI said, “We think this novel methodology has clear benefits of increasing sensitivity, cost and time savings for testing. The method stabilizes the RNA at room temperature for easier transport, storage, and handling in clinical settings.”

(Source: NIH, August 16, 2021)